<template>
  <div class="count">
    <h1>当前求和为: {{sum}}</h1>
    <select v-model.number="n">
      <option value="1">1</option>
      <option value="2">2</option>
      <option value="3">3</option>
    </select>
    <button @click="increment">+</button>
    <button @click="decrement">-</button>
    <button @click="incrementOdd">当前求和为奇数再加</button>
    <button @click="incrementWait">等一等再加</button>
  </div>
</template>

<script>
export default {
  name: 'count-com',
  data() {
    return {
      sum: 0, // 当前的和
      n: 1,    // 用户选择的数字
      canRun: true
    }
  },
  methods: {
    // 增加
    increment(){
      this.sum += this.n
    },
    // 减少
    decrement() {
      this.sum -= this.n
    },
    // 奇数 增加
    incrementOdd() {
      if( this.sum % 2 ) this.sum += this.n
    },
    // 等待 增加
    incrementWait() {
      Promise.resolve( new Promise( resolve => {
        resolve( this.throttle( () => {this.sum += this.n} ) )
      }))
      .then( val => {
        val()
        clearTimeout(val())
      })
    },
    // 节流
    throttle( fn ) {
      return () => {
        if (!this.canRun) return 
        this.canRun = false;
        var timer = setTimeout( () => {
          fn.call(this, arguments);
          this.canRun = true;
        }, 1000)
        return timer
      }
    }
  }
}
</script>

<style lang="sass">
$margin-left: 10px

button
  margin: $margin-left
</style>